📄 Chapter 4: Phase 1 Data Format

Foundation of Interoperability

Phase 1 of the WIA-FIN-005 standard establishes the foundational data formats that enable CBDC interoperability. Just as HTML provides a universal format for web pages regardless of the browser or operating system, Phase 1 provides universal data structures for CBDC transactions, wallets, and cryptographic operations.

Universal Transaction Schema

The core of Phase 1 is the Universal Transaction Format, which can represent any CBDC transaction while accommodating different architectural models.

Basic Transaction Structure

{
  "version": "1.0.0",
  "standard": "WIA-FIN-005",
  "transactionId": "tx_2025123100001234",
  "timestamp": "2025-12-25T10:30:00.000Z",
  "currency": {
    "code": "CNY",
    "cbdcId": "digital-yuan",
    "issuer": "PBOC"
  },
  "type": "transfer",
  "sender": {
    "walletId": "CN-1234567890",
    "publicKey": "02a1b2c3d4e5f6...",
    "signature": "3045022100..."
  },
  "recipient": {
    "walletId": "SG-9876543210",
    "cbdcId": "digital-sgd"
  },
  "amount": {
    "value": "1000.00",
    "precision": 2
  },
  "fee": {
    "value": "0.10",
    "payer": "sender"
  },
  "privacy": {
    "level": "standard",
    "technique": "zksnark",
    "proof": "..."
  },
  "metadata": {
    "purpose": "payment_for_goods",
    "reference": "INV-2025-001",
    "memo": "Coffee beans shipment"
  },
  "compliance": {
    "aml": true,
    "sanctions": "checked",
    "taxReporting": "required"
  }
}

Transaction Types

Wallet Format

WIA-FIN-005 defines a standard wallet format that supports both custodial and non-custodial models:

{
  "walletId": "CN-1234567890",
  "version": "1.0.0",
  "standard": "WIA-FIN-005",
  "cbdcId": "digital-yuan",
  "type": "non_custodial",
  "created": "2025-01-15T00:00:00Z",
  "owner": {
    "type": "individual",
    "verificationLevel": "tier2",
    "publicKey": "02a1b2c3d4e5f6...",
    "did": "did:wia:CN-1234567890"
  },
  "balance": {
    "available": "5000.00",
    "pending": "100.00",
    "locked": "500.00"
  },
  "limits": {
    "dailyTransaction": "10000.00",
    "singleTransaction": "5000.00",
    "monthlyVolume": "100000.00"
  },
  "features": {
    "offlinePayments": true,
    "smartContracts": true,
    "multiSignature": false,
    "crossBorder": true
  },
  "privacy": {
    "defaultLevel": "standard",
    "supportedTechniques": ["zksnark", "ring_signature"]
  }
}

Wallet Types

• Non-Custodial: User controls private keys directly
• Custodial: Third party (bank, payment service) manages keys
• Multi-Signature: Requires multiple signatures for transactions
• Smart Contract: Programmable wallet with embedded rules
• Hardware: Secure element-based offline wallet

Cryptographic Standards

Phase 1 specifies quantum-resistant cryptography as the default, with backward compatibility for current systems.

Signature Schemes

Hash Functions

• SHA3-256: Primary hash function for quantum resistance
• BLAKE3: High-performance alternative for large-scale operations
• SHA-256: Legacy compatibility (to be phased out by 2030)

Encryption

• CRYSTALS-Kyber: Quantum-safe key encapsulation (primary)
• AES-256-GCM: Symmetric encryption for data at rest
• ChaCha20-Poly1305: High-performance stream cipher alternative

Privacy Mechanisms

Phase 1 defines multiple privacy preservation techniques that jurisdictions can choose based on their regulatory requirements:

1. Zero-Knowledge Proofs

Allow transaction validation without revealing transaction details:

{
  "privacy": {
    "technique": "zksnark",
    "level": "high",
    "proof": {
      "type": "groth16",
      "publicInputs": ["commitment_root", "nullifier"],
      "proof": "0x1a2b3c4d...",
      "verificationKey": "0x5e6f7g8h..."
    },
    "reveals": {
      "amount": false,
      "sender": false,
      "recipient": true,
      "timestamp": true
    }
  }
}

2. Confidential Transactions

Hide transaction amounts using Pedersen commitments:

{
  "amount": {
    "commitment": "0x9a8b7c6d...",
    "rangeProof": "0x1f2e3d4c...",
    "blindingFactor": "hidden"
  }
}

3. Tiered Anonymity

Different privacy levels based on transaction characteristics:

Encoding and Serialization

WIA-FIN-005 specifies standard encoding formats for all data:

Transaction Encoding

• JSON: Primary format for API communication and human readability
• CBOR: Compact binary format for bandwidth-constrained environments
• Protocol Buffers: High-performance binary serialization for internal systems

Identifiers

{
  "walletId": "CN-1234567890",           // Format: {COUNTRY}-{NUMBER}
  "transactionId": "tx_2025123100001234", // Format: tx_{YYYYMMDD}{SEQUENCE}
  "cbdcId": "digital-yuan",               // Lowercase, hyphen-separated
  "did": "did:wia:CN-1234567890"          // Decentralized Identifier
}

Amount Representation

• Format: Fixed-point decimal string (never floating point)
• Precision: Specified per currency (typically 2-8 decimal places)
• Maximum: Configurable per CBDC (e.g., "999999999999.99")

Timestamp Format

• Standard: ISO 8601 with UTC timezone
• Example: "2025-12-25T10:30:00.000Z"
• Precision: Millisecond (3 decimal places)

Validation Rules

Phase 1 defines comprehensive validation rules that all compliant CBDCs must enforce:

Transaction Validation

1. Signature Verification: Valid cryptographic signature from sender
2. Balance Check: Sender has sufficient balance plus fees
3. Amount Validity: Amount > 0 and within limits
4. Timestamp Validity: Within acceptable clock drift (±5 minutes)
5. Nonce/Sequence: Prevents replay attacks
6. Format Compliance: All required fields present and correctly formatted
7. Privacy Proof: Valid zero-knowledge proof if privacy is enabled

Wallet Validation

1. Public Key Format: Valid for chosen cryptographic scheme
2. Checksum: Wallet ID includes error-detecting checksum
3. Unique Identifier: No duplicate wallet IDs in system
4. Verification Level: Matches declared transaction capabilities

Extensibility

Phase 1 includes extension mechanisms for future innovation:

Custom Fields

Implementations can add custom fields in designated extension spaces:

{
  "standard": "WIA-FIN-005",
  "type": "transfer",
  // ... standard fields ...
  "extensions": {
    "vendor": "central-bank-xyz",
    "customFields": {
      "riskScore": 0.12,
      "merchantCategory": "retail",
      "loyaltyPoints": 100
    }
  }
}

Version Compatibility

• Semantic Versioning: MAJOR.MINOR.PATCH format
• Backward Compatibility: Minor/patch versions are backward compatible
• Forward Compatibility: Unknown fields are ignored gracefully
• Version Negotiation: Systems negotiate highest mutually supported version

Reference Implementation

WIA provides open-source reference implementations in multiple programming languages:

TypeScript Example

import { WIACBDC, Transaction, TransactionType } from '@wia/cbdc';

const cbdc = new WIACBDC({
  cbdcId: 'digital-yuan',
  privateKey: '0x...'
});

// Create a transaction
const tx: Transaction = {
  type: TransactionType.TRANSFER,
  recipient: {
    walletId: 'SG-9876543210',
    cbdcId: 'digital-sgd'
  },
  amount: {
    value: '1000.00',
    precision: 2
  },
  privacy: {
    level: 'standard',
    technique: 'zksnark'
  }
};

// Sign and submit
const signedTx = await cbdc.signTransaction(tx);
const result = await cbdc.submitTransaction(signedTx);

console.log(`Transaction ID: ${result.transactionId}`);

Validation Example

import { validateTransaction, ValidationResult } from '@wia/cbdc';

const result: ValidationResult = validateTransaction(transaction);

if (result.valid) {
  console.log('Transaction is valid');
} else {
  console.log('Validation errors:', result.errors);
  // Example errors:
  // - "Invalid signature"
  // - "Insufficient balance"
  // - "Amount exceeds daily limit"
}

Testing and Compliance

WIA provides comprehensive test suites for Phase 1 compliance:

Test Categories

• Schema Validation: 150+ test cases for data format compliance
• Cryptographic Tests: Signature verification, hashing, encryption
• Privacy Tests: Zero-knowledge proof validation
• Edge Cases: Boundary values, malformed data, attack vectors
• Interoperability: Cross-CBDC transaction parsing

Certification Process

1. Self-Testing: Run open-source test suite against your implementation
2. Documentation: Submit implementation details and test results
3. Peer Review: Community review of implementation approach
4. Third-Party Audit: Independent verification of compliance
5. Certification: WIA certification badge and listing

Summary

Phase 1 provides the essential foundation for CBDC interoperability:

• ✅ Universal transaction format supporting all CBDC models
• ✅ Standardized wallet structures for custodial and non-custodial use
• ✅ Quantum-resistant cryptography for future-proofing
• ✅ Flexible privacy mechanisms respecting different regulatory approaches
• ✅ Clear validation rules ensuring security and correctness
• ✅ Extension mechanisms for innovation without breaking compatibility